Strange Error: DoesPackageExist: DoesPackageExist FAILED: '' is not a standard unreal filename or a long path name. Reason: Path should be no less than 4 characters long.

[UnrealEverything]

The error appears to be from a MathExpression node: https://github.com/EpicGames/UnrealEngine/blob/463443057fb97f1af0d2951705324ce8818d2■■■/Engine/Source/Editor/BlueprintGraph/Private/K2Node_MathExpression.cpp#L1829

Double check your blueprints where you use these node. If that doesn’t help try converting the expression to regular math nodes.